Method of purifying a lubricating oil feedstock with zinc halides



Patented Dec. 16, 1952 METHOD OF PURIFYING A LUBRICATING OIL FEEDSTOCKWITH ZINC HALIDES,

Thomas F. Rutledge, New

Castle, Del., and

Francis M. Seger, Pitman, N. 'J., assignors to Socony-Vacuum OilCompany, Incorporated, a

corporation of New York No Drawing. Application March 11, 1949, SerialNo. 81,013

3 Claims.

This invention has to do with the preparation of synthetic lubricantsfrom normal, alpha monoolefins and, more particularly, has to do withthe preparation of lubricants from certain complex mixtures containingsuch olefins.

As described in several related and co-pending applications, identifiedhereinafter, it has been found that normal, alpha mono-olefins of variedchain length can be converted to excellent synthetic lubricants. Highviscosity indices, low pour points and/ or superior stabilitycharacterize these lubricants. Not only have the individual normal,alpha mono-olefins proven of value in this regard, but mixtures of thesame have been found to be satisfactory. In addition, complex mixturescontaining substantial proportions of these olefins have been found tobe suitable starting materials. A source for the complex mixturescontaining these olefins is the Fischer-Tropsch process and relatedprocesses. As is Well known in the art the Fischer-Tropsch processinvolves reaction of carbon monoxide and hydrogen in the presence ofcobalt or chemically related catalysts, whereupon hydrocarbons,including olefins and paraflins, and oxygen-containing compounds areformed. When iron catalysts are used in place of cobalt, and/or whenlarger carbon monoxide to hydrogen ratios are used, larger quantities ofoxygen-containing compounds are generally formed.

While the foregoing complex mixtures are converted to syntheticlubricants of low pour point, high viscosity index and good stability,as described in the applications referred to above, cer-' tainconstituents therein are deleterious in reducing the yield and/orquality of the lubricants. Undesirable constituents include non-primaryolefins, aromatics, naphthenes and parafiins; oxygen-containingcompounds; suspended material, particularly metallic catalysts and theircompounds. With regard to quality of the lubricants, it has been foundthat considerable color characterizes the lubricants. This is a seriousshortcoming inasmuch as the highly colored lubricants generally do notrespond to conventional procedures, namely, filtration, adsorption,etc., for removing color bodies. In addition, the carbon residue valuesof the lubricants are relatively high. A further shortcoming, traceableto constituents of the complex olefinic charge stocks, is that theviscosity indices of the lubricants generally fall below those of thelubricants formed from individual normal, alpha mono-olefins. Stillanother undesirable feature is in the relatively low response of thelubricants to inhibitors, particularly oxidation inhibitors. This iswell illuscomprising an oil-soluble, p'ho'sphoru'sand "sulfur-containingreaction product of plnene and phosphorus pentasulfide, which isdescribed in detail in Patent No. 2,416,281 and in copending applicationSerial No. 482,482, filed April 9,1943.

It has now been found that synthetic lubricants of good color and. lowcarbon residues can be obtained by treating the foregoing complex olefincharge stocks with zinc chloride, distilling off the olefinic materialfrom the resultant mixture and converting the olefinic material tosynthetic lubricants by the procedures described in the followingcopending applications.

In copending application Serial No. 761,716, filed July 17, 1947, nowabandoned in favor of application Serial No. 104,932, filed July 15,1949, which matured into U. S. Letters Patent No. 2,500,166, issuedMarch 14, 1950, it has been shown that normal, alpha mono-olefins havingsix to twelve carbon atoms per molecule form synthetic lubricants whenheated at 500-750 F. in the absence of a catalyst (particularly of theFriedel- Crafts type). At temperatures of the order of 700-900 F., theuse of a gas such as hydrogen, carbon monoxide and mixtures of suchgases, with the aforesaid mono-olefins makes possible the formation ofsynthetic lubricants in substantial yield. This is described incopending application Serial Number 6,814, filed February 6, 1948, nowPatent No. 2,500,159, issued March 14, 1950. The aforesaid mono-olefinsare also converted to synthetic lubricants when contacted with leadtetra-acetate at elevated temperatures, particularly 400-700 asexplained in copending application Serial Number 44,403, filed August14, 1948, now Patent No. 2,500,161, issued March 14, 1950. Anotherrelated development involves condensation, at 500-750 11, of an olefinmixture comprising a short chain, mono-olefin of two to six carbon atomsand a long chain normal, alpha mono-olefin of ten to thirty carbonatoms; the mean carbon chain length is maintained Within the range ofsix to twelve carbon atoms by proper proportioning of the clefins. Thisis described in copending application Serial Number 47,556 filedSeptember 2, 1948, now Patent No. 2,500,162 issued March 14, 1950.

Polymerization of the aforesaid mono-olefins of six to fourteen carbonatoms per molecule, in the presence of a paraffin at temperatures inexcess of 700 F., forms the subject matter of copending applicationSerial No. 86,384, filed April 8, 1949, now Patent No. 2,500,165 issuedMarch 14, 1950. Mcnocyclic aromatics and/or naphthenes may be used inthis polymerization, in place of the paraffin, as shown incopendingapplicationSerial No. 88,895, filed April 21, 1949, now

Patent No. 2,500,244 issued March 14, 1950. Polymerization of saidmono-olefins may also'be accomplished at temperatures within the range550-750" F. by using small amounts of sulfur, selenium and/or tellurium;this is described in copending application Serial No. 63,204, filedDecember 2, 1948, now Patent No. 2,500,164 issued March 14, 1950. Attemperatures of the order of SOD-750 F., small amounts of phosphorussulfides affect the polymerization of the aforesaidmonoolefins; this isdescribed in copending application Serial No. 57,421, filed October 29,1948, now Patent No. 2,500,163 issued March 14,1950. 7

A catalytic conversion of normal, alpha monoolefins having from five toeighteen carbon atoms to synthetic lubricants is described in copendingapplication Serial No. 776,428, filed September 26, 1947, now abandoned;the catalysts used are silica-alumina composites.

Styrene also reacts with the aforesaid monoolefins, at temperatures fromabout 500 F. to about 700 F. with the formation of synthetic lubricants,as shown in copending application Serial No. 6,993, filed February 7,1948, now Patent No. 2,500,160 issued March 14, 1950. Conjugatedhydrocarbons and sulfur react with normal, alpha mono-olefins havingfrom about five to about eighteen carbon atoms to form lubricants;copending application Serial No. 33,438, filed June 16, 1948, now PatentNo. 2,500,167 issued March 14, 1950. A related development involvesreaction of conjugated hydrocarbons, phosphorus sulfides and thecorresponding mono-olefins of six to fourteen carbon atoms, as shown incopending application Serial No. 64,904, filed December 11, 1948, nowPatent No. 2,500,247 issued March 14, 1950. Still another relateddevelopment is that wherein lubricants are formed by reaction ofvinyl-substituted aromatic compounds, thiols and normal, alphamono-olefins, described in copending application Serial No. 97,921,filed June 8, 1949, now Patent No. 2,500,672 issued March 14, 1950.

In copending application Serial No. 673,892, filed June 1, 1946,, nowPatent No. 2,551,638, issued May 8, 1951, it is shown that normal, alphamono-olefins having from about seven to about twelve carbon atoms permolecule react with organic peroxides at 120-570 F. to form syntheticlubricants. With the corresponding mono-olefins of six to eighteencarbon chain length, organic peroxides and halogenatedolefins arereacted at 120-570 F. with the formationof lubricants; Serial No.776,427, filed September 26, 1947, now Patent No. 2,551,640, issued May8, 1951. As a related development, organic peroxides, conjugatedhydrocarbons and the aforesaid mono-olefins of from five to eighteencarbon atoms are reacted at 120570 F. to form lubricants; Serial No.53,372, filed October 7, 1948, now Patent No. 2,551,641, issued May 8,1951. Organic peroxides, aromatic hydrocarbons and said mono-olefins ofsix to fourteen carbons also react to form lubricants, as described incopending application Serial No. 72,744 filed January 25, 1949, nowPatent No. 2,551,642, issued May 8, 1951. Certain heterocyclic compoundsmay be used in place of the aromatic hydrocarbons in the last-mentioneddevelopment; this is explained in copending application Serial No.83,772 filed March 26, 1949. Lubricantsof high viscosity are formed byreacting the aforesaid mono-olefins of six to fourteen carbon atoms withcertain unsaturated esters and organic peroxides; copending applicationSerial No. 72,745 filed September 23, 1949, now Patent No. 2,551,643issuedMay 8, 1951.

Normal, alpha mono-olefins also react with olefinic mono-oxides and-,sulfides at 500-700 F. to form lubricants, as explained in copendingapplication Serial No. 750,170, filed May 23, 1947, now Patent No.2,486,441 issued November 1, 1949.

It is to be understood, therefore, that the treated, complex olefiniccharge may be converted to synthetic lubricants by any of the foregoingconversion procedures shown in the aboveidentified applications.

ZINC CHLORIDE: TREAT As indicated above, zinc chloride is used intreating the complex olefinic charge stock. Zinc fluoride, bromide andiodide are of the same chemical class as the chloride and may be usedherein; however, in view of the much lower cost and greater availabilityof the chloride, the latter is most advantageous herein. The chloride ispreferably used in anhydrous form, although satisfactory results arealso obtained with a chloride containing some Water. In fact, aqueoussolutions of zinc chloride are suitable such as a saturated solution atC. containing 615 grams ZnClZ per 100 parts of water; but, ordinarily,the water is removed by distillation in the treating procedure and istherefore not desired in the charge.

The amount of zinc chloride may be varied widely, depending upon theform of the chloride, the particular olefinic charge stock and thetreating conditions. Quantities from about 0.5 per cent to 20 per centor more of chloride, by weight, based upon the quantity of olefiniccharge stock, are employed.

Treating temperatures may be varied considerably. Preferred, though, aretemperatures of reflux of the olefinic charge, either at atmospheric,reduced or elevated pressure. Reflux temperatures make possible removalof any water of reaction, causing a more favorable equilibrium invarious condensation and/or polymerization reactions catalyzed orinduced by the solid acidic treating agent. Whatever the reactionmechanism, however, the olefinic content of the charge is not affectedappreciably.

It will be clear that the zinc chloride treatment may be carried out inbatch operation, as in a reaction vessel equipped with suitabledistillation equipment. For example, the olefinic charge may be slowlydistilled over the chloride, or may be heated with said compound for alonger period, e. g., several hours, and then flash distilled. It isalso to be understood that the treat may be carried out in continuousoperation, in which case the chloride and the olefinic charge stock mayflow in concurrent or counter-current relationship to each other in areaction vessel. It is preferred that the chloride be in finelydividedform in such operations. In all cases, agitation of the olefinicmaterial and treatin agent, or other means for providing intimatecontact, is recommended.

Following treatment of the complex olefinic charge with zinc chloride,the treated charge is dis-tilled. This distillation removes any reactionpro-ducts which may dissolve in the excess hydrocarbon present. Thedistillate is a material containing purified and concentrated olefins,particularly normal, alpha mono-rolefins. The distillate fractionboiling from about 100 F. to about 600 F.. and boiling predominantlywithin the range -500 F., is taken overhead.

7 It will. be apparent from the discussionof the zinc chloride treat andfrom the earlier discussion of the conversion processes contemplatedherein that the treated olefinic charge stocks should contain normal,alpha mono-olefins havally not improved. Aluminum chloride, which hasbeen used considerably in hydrocarbon treatments, has proven to beundesirable in the procedure contemplated herein. As demonstrated ingfrom about six to twelve, fourteen or eighteen 5 hereinafter, A1013 doesnot improve the color or carbon atoms depending upon the conversioncarbon residue values, but actually has a deleprocedure. Accordingly,the predominant porterious effect. Ferric chloride, too, is of littletion of the treated olefinic mixture should boil value. above about 145F., the boiling point of n-hexene-l, with the maximum boiling point ofthe 10 EXAMPLES treated mixture being not substantially greater Thefollowing specific examples serve to illusthan the boiling point of anormal, alpha monotrate, and not limit, the invention. In all examolefinof fourteen, sixteen or eighteen carbon ples, the olefin charge stocksused were obtained atoms. It will also be apparent that the boiling fromFischer-Tropsch reactions wherein iron range of the untreated olefinicmixture may be catalysts were used. In Examples I-X, theconsiderablywider than that of the treated mixcharge stock had a boilingrange of 200-300 F., a ture which is converted in the aforesaidprocespecific gravity of 0.7559, and contained a predures. The minimumboiling point may be well dominant quantity of normal, alphamono-olebelow that of the distillate fraction to be confins of seven tonine carbon atoms; in Examples verted, and the maximum boiling point ofthe un- XI-XIV, the stock had a boiling range of 300-450 treated mixturemay be somewhat higher than F., a specific gravity of 0.8003, and themono-olesaid distillate fraction. With regard to the unfins were mainlyof nine to twelve carbon atoms; treated mixture, it is generallyadvisable to suband in Examples XV-XVI, the boiling range was ject thecrude olefinic mixture from the Fischer- 150-5l0 F., specific gravity,0.7766, and the num- Tropsch process to a preliminary distillation, berof carbon atoms of said mono-olefins was prior to the zinc chloridetreat. In this distillafrom six to fourteen. The quantity of chargetion, gross contaminants such as iron particles stock in each examplewas 500 parts by weight. and high boiling waxy materials are removed, Inthe examples wherein a metal halide was and a distillate fraction of theselected boiling used, the olefinic charge and the halide were range istaken. mixed and the charge refluxed at atmospheric While filtration ofthe charge, prior to distilressure for 1-4 hours, except as indicatedotherlation, is not essential, it is a desirable procedure. Wise. Themixture 'was vigorously stirred during With filtration, any occludedsolid particles are refluxing and the refluxing was accompanied byremoved. water removal. The residual halide was removed In contrast tothe zinc chloride treat and its by filtration and the filtrate wasdistilled. The infiuence upon the synthetic lubricants formed distillatewas then converted to a synthetic lubrifrom the treated stocks aretreatments with other cant when heated in a bomb, at 625 or 650 F. asmetal halides. Calcium chloride, for example, indicated, for ten hoursin an atmosphere of nihas been found to be of little or no value in suchtrogen, as described in detail in said copending a treat. While someimprovement in viscosity 40 application Serial No. 761,716. index may berealized when calcium chloride is Pertinent data for the examples areset forth used, carbon residue and color values are generin Table I.

TABLE I Pretreatment of olefinic charge stocks with metal halides Run N0I II -III Iv v VI VII vnr Bgilling range ofstock used, 200-300 200-300200-300--.. 200-300.--- 200-300 200-300 200-300 200-300 PretreatmentFiltered Distilled only. CaOlz-l-HCI A1013 (1%) A1013 only. (1%)- (1%)-Temperature, C 110 29 (liq.). Time, hours l. 2. Water removed, parts 4.0None by weight. Redistillation,F 200-290.-.- 200-294."- 200-300 200-280200-300 200-302 Distillate color W.white Yel1ow. Pale yellow Paleyellow- Pale yellow. Yellow Material balance:

Redisttilled charge, per- 70.0 89.0 80.0 79.0 89.0 02.0 Dfs tailtlationresiduapen 12.8 6.05 2.4 5.2 7.8 4.8. 'i liosse ercentun 11.24.95 17.0 15.8 3.2 33.2. Distillate inspections:

Bromi(1i1)e number (Nor- 99.9 97.7 104.8 100.7 99.5 102.4. sggcfitcgmvt0.7491. 0.7515. 0.8348 0.7519 01519.1"--. 0.7511 Conversion:

Marxsimum pressure Oil yield, wt. percent of treated hydrocol charge.Residual oil:

Color, lovibond Carbon residue, Ramsottom. Specific gravity.-- Pourpoint, F"... K. V., centistokes a 210F Viscosity index 1 Abnormal lossesin bomb.

TABLE IContinued Pretreatment of olefim'c charge stocks with metalhalides Run No IX X XI XII XIII XIV XV XVI Boiling range of stock used,200-300---- 200-300-.-- 300-450 300-450 300450 300450 150-509.- 150-509.Pretreatment Fe???) BEE-$33711) Reiiluzxed and ZnClz(1%).. ZnOlz(2%)..FeCh(1%). None Z1101: (1%).

Temperature,0 1101..." 29 (111 5... 176.7 (liq)- 149 117 (1lq.)-- 176.7(liq.)- Time,hours 1 1 2 4. Water removed, parts 2.9 None- 1.0.

byweight. Redistillation, F 200-300.--. 200-310 300-421 Distillate colorW.'white W.white Yellow Material balance:

Rcdisttllled charge, per- 89.0. 86.0 87.4

cen Distillation residue, per- 5.0 5.4 9.65

cen Total losses, percent. 6.0 8.6 2.95 Distillate inspections:

Bromidn)e number (Nor- 1019..-... 101.0 73.4

woo Specific gravity 0.7519.-- 0.7479--- 0.8003 Conversion:

Maximum pressure 1,650 1,450 300 (PSI). Oil yield, wt. percent 18.5 1634.1

of treated hydrocol charge. Residual oil:

Color, lovibond l4 7. Carbon residue, Rams- 0.09 0.04. bottom. I

Specific gravity 0.8458. 0.8628. Pour point, F (-30.

K. V., centistokes at- Viscosity index 105 .3.

2 Slow distillation over solid ZnClz, variable temperature.

Considering the foregoing data for Examples I-IV, it will be noted thatthe sequence of zinc chloride treat, distillation and conversion of distillate make possible the production of a superior lubricant. Theexample, the viscosity index values (V. I.) of the lubricants identifiedas Examples III and IV are 104 and 99, respectively; Whereas, the V. I.,of Examples I and II are only 92 and 96, respectively. In thisconnection, it should .be noted that V. I. values are accurate to about12% (this includes normal variation in polymerization step, etc). Thedata also reveal a substantial color improvement, 1.2 and 5.0 for theoils of Examples I11 and IV, respectively, compared with 48 and 13,respectively, for the oils of Examples I and II. Substantial reductionin carbon residue is also shown by Examples III and IV.

The effect of other metal halides is shown by Examples V-X. Calciumchloride is shown in Examples V and VI, demonstrating improvement in V.I. but less desirable color and carbon residue values. Examples VII andVIII reveal that aluminum chloride may have an adverse efiect or animproving effect upon V. I., but greatly depreciates the color andcarbon residue values. Ferric chloride is shown in Example IX; noimprovement in carbon residue is realized and there is but slightimprovement in V. I.

Examples XI-XIV involve a different fraction of olefinic stock, with theresults similar in character to those of Examples I-X.

The value of slowly distilling an olefinic charge stock over zincchloride is shown by Examples XV and XVI.

It is to be understood that the foregoing specific treating conditionsand examples serve to illustrate the invention, for it will be apparentto those skilled in the art that modification and variations thereof maybe used. It is to be under-' stood, therefore, that such modificationsand variations fall within the scope of the appended claims, and thatthe invention is to be construed broadly in the light of the language ofthe claims.

We claim:

1. The process for preparing a synthetic lubricant having good color,low carbon residue and high viscosity index, which comprises: contactingwith a zinc halide an olefim'c charge stock obtained by aFischer-Tropsch reaction, a sub stantial portion of said stock boilingwithin the range of about F. to about 500 F.; distilling said treatedstock and collecting an olefinic distillate boiling predominantly withinthe range of about 150 F. to about 500 F.; and converting saiddistillate into said synthetic lubricant.

2. The process of claim 1 wherein the halide-is zinc chloride.

3. The process of claim 1 wherein the distillate is converted into saidsynthetic lubricant by heating the same at a temperature of about 625 F.for about ten'hours.

THOMAS F. RUTLEDGE. FRANCIS M. SEGER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS I Heinrich et a1. May 9, 1950

1. THE PROCESS FOR PREPARING A SYNTHETIC LUBRICANT HAVING GOOD COLOR,LOW CARBON RESIDUE AND HIGH VISCOSITY INDEX, WHICH COMPRISES: CONTACTINGWITH A ZINC HALIDE AN OLEFINIC CHARGE STOCK OBTAINED BY AFISCHER-TROPSCH REACTION, A SUBSTANTIAL PORTION OF SAID STOCK BOILINGWITHIN THE RANGE OF ABOUT 150* F. TO ABOUT 500* F.; DISTILLING SAIDTREATED STOCK AND COLLECTING AN OLEFINIC DISTILLATE BOILINGPREDOMINANTLY WITHIN THE RANGE OF ABOUT 150* F. TO ABOUT 500* F.; ANDCONVERTING SAID DISTILLATE INTO SAID SYNTHETIC LUBRICANT.